Collecting Photons


A systems view of photography would have one think holistically of the entire photographic process, rather than the single obvious step: push the shutter button.  

Several things happen before one pushes the shutter button and after. Each of these things influences the final outcome.  Understanding these relationships can change how one approaches each step.  Here I explore the relationship between capture and post processing of the digital image. 

In a systems view one could look at the camera as a photon capture device and the post-processing software as the image developing device.  The primary role of the camera is in this scenario to capture as much light (photons) as possible so that the post processing software has a good sample set to work with.  Some photographers go further and put it in terms of information collection and processing; the more information one captures about a scene the more that can be processed subsequently.

In digital photography there is a guideline: capture to the right. When you capture to the right you collect the most number of photons, which equals information.  This guidance is referring to the curve presented in the on-camera histogram and recommends it should have its peak to the right of centre. To fully appreciate this guidance one needs to understand the role of the histogram and how it reflects what the camera sees. A fuller discussion can be found on DP Review, but simply put the histogram replaces the light meter and informs the photographer of the available light.  But it adds two other pieces of information: (1) how that light is distributed from dark (on the left) to light (on the right) (2) whether the image is over or under exposed.

In the last month I have been experimenting with this technique and trying to apply the guideline.  Obviously it becomes important that the histogram accurately reflects the distribution of available light.  It turns out that in most case the histogram reflects not the “raw” data but rather a processed view of the data (i.e., the current settings such as vibrant, nature, nostalgic, etc.).  

post I came across discussed this issue and suggested ways of getting more accurate histograms. The author of the post suggested reducing some of the settings (saturation and contrast) and resetting the white balance. Taking this step dramatically changes the image displayed on the back of the camera after each shot, yet the results after post processing are quite good. 

[left] As captured in camera [right] after post processingI shall continue with this experiment.


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